1. Field of the Invention
The present invention relates generally to digital computer bus architecture and, in particular, to a slave controller for controlling transfer of digital data to and from a slave such as a memory via the VMEbus (VERSA MODULE EUROPE bus).
2. Background of the Invention
The proliferation of microprocessors has produced the economic incentive and consequent trend to construct modular multimicroprocessor computer systems, where implementations use one high performance processor. Such modular systems are facilitated by a bus structure, referred to as a backplane bus, to which microprocessors, system controllers, data storage modules, input/output controllers and associated peripheral devices can be connected and through which each device on the bus can communicate with other devices on the bus.
The main purpose of any bus structure is to allow devices connected to the bus structure to transfer data from one device to one or more of the other devices in accordance with a predetermined protocol of communication. A "standard" bus is one for functional, electrical and mechanical requirements for interface circuits and a set of signal lines that constitute the bus which are determined for all devices connected to the bus. Generally, the signal line groupings on standard backplane buses are partitioned into logical groupings that comprise a data transfer bus having address and data lines; an arbitration bus having control and acquisition lines; and a utility bus which includes power leads and on some buses, clock signals, initialization and power lines.
The VMEbus is one such standard bus which is well known and very popular in automated manufacturing and processing environments. The VMEbus has a 16/32 backplane bus, the aforementioned signal line groupings and a priority interrupt bus which provides the signal lines needed to generate and service interrupts. The VMEbus is set forth the "VMEbus Specification Manual", Revision C.1, dated Oct. 1985, published by Motorola.
In the past connecting a device such as a memory board to the VMEbus generally required the user to purchase a board or multiple boards which provide the necessary backplane interface logic and functional logic to allow the device to interface with the VMEbus. These boards are often expensive, complex in design and generally are limited to single function, such as, allowing a data storage device having a predetermined storage capacity to interface with the VMEbus. With these and other disadvantages known to backplane interface and functional logic boards for use with the VMEbus the present invention was conceived and one of its objectives is to provide a simple and inexpensive slave controller which will allow a device such as a memory to interface with the VMEbus.
It is another object of the present invention to provide a single chip controller to replace the backplane interface logic and the functional logic currently used to interface a device such as a memory with the VMEbus.
Various other advantages and objectives of the present invention will become apparent to those skilled in the art as a more detailed description of the present invention is set forth below.